Merge pull request #4103 from atom/ns-fix-active-pane-deserialization

Make deserialization of the active pane more tolerant and add assertions to catch invalid states

spec/pane-container-spec.coffee

@@ -33,6 +33,13 @@ describe "PaneContainer", ->
       [pane1B, pane2B, pane3B] = containerB.getPanes()
       expect(containerB.getActivePane()).toBe pane3B
 
+    it "makes the first pane active if no pane exists for the activePaneId", ->
+      pane3A.activate()
+      state = containerA.serialize()
+      state.activePaneId = -22
+      containerB = atom.deserializers.deserialize(state)
+      expect(containerB.getActivePane()).toBe containerB.getPanes()[0]
+
   it "does not allow the root pane to be destroyed", ->
     container = new PaneContainer
     container.getRoot().destroy()

src/pane-container.coffee

@@ -40,6 +40,8 @@ class PaneContainer extends Model
     @registerViewProviders()
 
     @setRoot(params?.root ? new Pane)
+    @setActivePane(@getPanes()[0]) unless @getActivePane()
+
     @destroyEmptyPanes() if params?.destroyEmptyPanes
 
     @monitorActivePaneItem()
@@ -137,6 +139,9 @@ class PaneContainer extends Model
 
   setActivePane: (activePane) ->
     if activePane isnt @activePane
+      unless activePane in @getPanes()
+        throw new Error("Setting active pane that is not present in pane container")
+
       @activePane = activePane
       @emitter.emit 'did-change-active-pane', @activePane
     @activePane

src/pane.coffee

@@ -502,6 +502,8 @@ class Pane extends Model
 
   # Public: Makes this pane the *active* pane, causing it to gain focus.
   activate: ->
+    throw new Error("Pane has been destroyed") if @isDestroyed()
+
     @container?.setActivePane(this)
     @emit 'activated'
     @emitter.emit 'did-activate'